I think what LESTER is referring to is condition, it may be functional but it's in fairly bad condition. The pitting itself is really bad, if your photos indicate before and after, it looks like it spent decades sitting on a coral reef.
You posted a link to a pistol in near pristine condition hence the price. However even at auction an item will only sell for what a given buyer is willing to pay. If you had some provenance to accompany the pistol it might help with valuation.
It would appear you're in Austria, selling/transferring a firearm to a US based private buyer could prove difficult.
Best advice, find a local expert in antique firearms. Good luck!